Understanding Fire Requirements

Again, the primary aim of fire requirements is occupant safety: ensuring that a fire is contained long enough to allow occupants to escape the building and to prevent structural collapse. Building materials and assemblies are tested and rated for different qualities related to their performance in a fire. Though they may sound similar, these terms have specific meanings which are important to understand when specifying building materials.

Combustible and Noncombustible Materials

By definition, a noncombustible material is one of which no part will burn or ignite when subjected to fire or heat. Materials that pass ASTM E 136 are considered noncombustible. Examples of noncombustible materials include masonry, stucco, and mineral fiber insulation. In addition, materials consisting of a structural base of noncombustible material with a surfacing material no more than ¹/₈ inch (3.2 millimeters) thick, which has a flame spread index (FSI) of 50 or less, are also considered noncombustible. An example of the latter is fiberglass batts with Class A rated facings.

ASTM E 136: Standard Test Method for Behavior of Materials in a Vertical Tube Furnace at 750 degrees Celsius is the test used to determine noncombustibility. For this test, a tube furnace is pre-heated to a temperature of 750 degrees Celsius. A preweighed material specimen is lowered into the furnace with one thermocouple attached to its surface and another located at its center. Testing continues until both thermocouples have stabilized at a maximum reading or until one of the acceptance criteria is violated. A material is rated as either “pass” or “fail.”

Fire Resistance

This term is typically used to characterize building assemblies. A fire-resistance rating refers to the period of time a building element, component, or assembly maintains the ability to confine a fire, continues to perform a given structural function, or both.

ASTM E 119: Standard Test Method for Fire Tests of Building Construction and Materials is used to evaluate fire resistance. An assembly or structural member is placed in a flat furnace in either the horizontal or vertical position and subjected to specific load (if a load-bearing element). The specimen is then subjected to a controlled flame, the temperature of which is increased along a specific time-temperature curve. The test continues until either structural collapse occurs; the temperature rise of the unexposed surface of the assembly exceeds 250 degrees Fahrenheit from ambient; or cotton waste placed on the unexposed side of the assembly is ignited by radiant heat. The assembly is classified based on time expired before failure. For example, a 1-hour fire-resistant assembly will withstand fire exposure for 1 hour before the structural integrity of the wall fails. As was mentioned earlier, fire-resistive glass can be part of 1- or 2-hour wall assemblies that require meeting ASTM E-119. Fire-protective glass, though it can have fire ratings up to 3 hours, cannot be used in such assemblies because it does not meet the ASTM E-119 wall criteria, specifically the radiant heat transfer requirements.

Image courtesy of SAFTI FIRST Fire Rated Glazing Solutions

This diagram illustrates the attributes of fire-protective glass, which contains flames and smoke but does not block radiant heat.

Image courtesy of SAFTI FIRST Fire Rated Glazing Solutions

Fire-resistive glass, on the other hand, contains flames and smoke and limits the transmission of radiant heat, and so can be included in assemblies rated for 60 minutes or more.

Going Beyond Code: Building For Resilience

It’s worth reiterating that building codes were developed to provide life safety. They are often based on historical data and do not ensure that buildings ultimately survive a disaster with little damage—or that they survive at all.

In the last several years, the concept of resilient buildings has gained more traction. In its 2015 Summit on Resilience, the American Institute of Architects (AIA) defines resilience as “the ability to prepare and plan for, absorb, recover from, and more successfully adapt to adverse events.”

A resilient building not only protects occupants during a disaster, it is able to maintain critical services during that time. There’s a financial argument for resilient buildings too, as a more resilient building will be able to bounce back from disasters more quickly and avoid business interruption and/or costly repairs.

Designed in are contingency measures for supplying power and water, if not to the entire building, to crucial equipment, and redundancies that ensure that if one system fails, another can take over. A resilient building does not exist in a vacuum; instead, it can share services with other buildings, serve as a safe refuge, and even help reduce the impact of certain hazards through its design and site features.

Let’s look at the four examples introduced earlier to illustrate how architects can specify products and systems that make buildings more resilient while mitigating specific hazards and meeting other project goals.

Expansion Joint Covers and the Seismic Hazard

Expansion joint covers can be installed inside and outside a building and cover the expansion joint itself. These covers can expand and contract to accommodate extreme seismic activity.

Expansion joint covers are designed to blend into surrounding floor materials without posing a tripping hazard. They are durable and can be designed to stand up to the heavy foot traffic typical in commercial and institutional buildings, or to withstand heavy rolling loads such as emergency vehicles and maintenance equipment (lifts and carts).

Seismic expansion joint covers are incorporated into buildings to accommodate potential movement in the event of an earthquake. Unlike thermal expansion joint covers, which are used to accommodate smaller scale expansion and contraction due to temperature changes, seismic expansion joint covers must also be able to accommodate lateral shear and vertical displacement—the up-and-down and side-to-side movements experienced during an earthquake. The expansion and contraction capabilities of seismic cover systems ensures that building occupants can safely exit the building during an event, maintains access for emergency services after the event, and may also save a building from being severely damaged or destroyed. Seismic cover systems require careful engineering to ensure they can accommodate the expected movement while also meeting the requirements for fire separation, safety, and aesthetics.

“In areas with seismic movement, expansion joint covers are designed for worst-case scenarios and are used in buildings with the risk of encountering dramatic movement caused by earthquakes,” says Dan Chapman, senior manager, product marketing, Construction Specialties.

Expansion joint covers can be customized to accommodate a building’s unique configuration and requirements for movement while fulfilling the architect’s aesthetic goals.

Formaldehyde-Free Mineral Wool Insulation

Made from inorganic materials, mineral wool is naturally noncombustible and has a high melting point; therefore, it will retain its shape longer when exposed to extreme heat. Hence, mineral wool can play a vital role in fire-resistant assemblies that help contain a fire. It also can be used as continuous exterior insulation and as a firestop around joints and penetrations. However, until recently, all mineral fiber manufacturers used small amounts of formaldehyde binder in their products. Formaldehyde is a volatile organic compound (VOC) that can affect indoor air quality.

Responding in part to the demands of the building industry, some manufacturers have begun offering formaldehyde-free mineral wool products. The availability of these products will enable building designers to specify products that meet all of the criteria for their high-performance and resilient projects, including fire resistance, energy performance, and indoor air quality.

“Removal of all harmful ingredients and chemicals should be a priority for all manufacturers of building materials and products,” says Matt St. Pierre, quality control coordinator, Integrated Eco Strategy. “Formaldehyde-free mineral wool has really revolutionized the market. Integrated Eco Strategy is more than thrilled to recommend these products for our current and future Living Building Challenge (LBC) projects, and all buildings would benefit from its use over formaldehyde-containing mineral wool.”

In addition to its noncombustibility, mineral wool offers other benefits. Because of its density, mineral fiber offers outstanding acoustic mitigation. And, because the material is hydrophobic—i.e., because it doesn’t “like water”—mineral wool sheds moisture, discouraging mold growth, and it doesn’t degrade when exposed to moisture. Mineral fiber insulation products also are made with up to 70 percent recycled content, and so they can help satisfy project goals around responsible resource use.

Some manufacturers offer guidance for installing mineral fiber insulation as part of an assembly and even offer complete fire-resistant assemblies that include mineral fiber, easing the burden on the architect.

Disaster-Proof Window and Door Assemblies

Openings are typically vulnerable points in the envelope. For example, glazing can break when exposed to the heat stress of a fire, allowing a fire to penetrate a room. During tornadoes, typhoons, and hurricanes, wind-borne debris can break windows, and once a building envelope is breached, wind forces or pressures inside a building increase dramatically. High wind pressures can rip windows and doors off their anchor points and/or expose weaknesses that allow water to enter. Even if windows and doors remain in place, leakage—due to poor flashing or weatherstripping, improper installation, or weaknesses in the connections between frame and door or glazing—can allow water to enter a building’s interior, even when the structure of the window or door remains intact.

Window and door assemblies that resist these forces are key components in resilient building envelopes. Most products required for resilient design needs to be furnished as assemblies rather than individual components—windows and doors, for example, include the framing and hardware in addition to the glazing and door panels. These assemblies as a whole are tested to verify their performance during disasters. Such tests simulate the conditions found during various man-made and natural disasters, such as fires, bomb blasts, and tornadoes.

Responding to these complex demands, manufacturers have developed products that can mitigate one or more categories of disasters and meet the criteria of all relevant tests. These products are typically aesthetically indistinguishable from conventional versions and still offer the performance benefits that help meet other projects goals. Let’s look at a few examples.

Fire-Resistive Glazing Systems

At least one manufacturer offers fire-resistive glazing systems that also can provide the desired levels of impact resistance, daylighting, and energy performance. These systems consist of fire-resistive glass and framing systems that are rated for up to 2 hours as per ASTM E-119. Fire-resistive glazing contains smoke and flames and blocks radiant heat as well, forming a “transparent wall” that allows occupants to safely exit the building or provides a safe haven from the fire; it also can help keep firefighters safe as they rescue occupants and extinguish the fire. To ensure their performance under other conditions, the framing systems are validated with static and dynamic water pressure testing; air infiltration testing; thermal cycling and condensation testing; and structural and seismic and interstory displacement testing. The systems even can be customized to be bulletproof up to Level 8, as validated by UL 752-2005.

Such an example highlights the complexity of the demands placed on the building envelope (and the architect or designer) as well as the benefits of working with a manufacturer dedicated to technical support, transparency, and third-party validation of its products.

Disaster-Proof Doors

Certain types of buildings or portions of buildings may require door systems that can withstand extreme impacts and/or wind pressures, whether from a natural disaster such as a tornado or an explosive blast or bullet impact associated with a terrorist attack. Two examples of buildings that require such door systems include safe rooms and those buildings identified in the DoD Minimum Antiterrorism Standards, UFC 4-010-01.

A safe room, as defined by FEMA, is an interior room, a space within a building, or an entirely separate building designed and constructed to provide near absolute life-safety protection for its occupants from tornadoes or hurricanes. Safe rooms also can serve to protect against man-made disasters, such as bomb detonations.

Guidance for designing safe rooms can be found in FEMA 361: Safe Rooms for Tornadoes and Hurricanes, which applies to safe rooms in buildings with occupant levels of 16 or more. FEMA 361 references ICC 500: Standard for the Design and Construction of Storm Shelters, which includes impact and pressure performance criteria for openings.

Another resource is the Interagency Security Committee (ISC) Design Criteria DoD Minimum Antiterrorism Standards (UFC 4-010-01), which was developed by the DoD in an effort to reduce the risk of mass casualties from terrorist attacks in the buildings in which DoD staff live and work. As such, it is the accepted standard for any building owner seeking to reduce the vulnerability of building occupants to terrorist attacks. Among other things, this standard establishes criteria for both glazing systems and doors and the types of blasts they must be able to withstand and the acceptable level of damage sustained. Exterior doors are tested for blast resistance in accordance with ASTM F2247, ASTM F2927, and ASTM F1642.

In addition, some project owners may want to protect building occupants from gunfire by specifying bulletproof doors. Of course, ballistic impacts vary widely depending on the weapon used. UL 752 is the test used to determine the level of bullet resistance required. The test defines 10 levels of bullet resistance, ranging from Level 1 (must be able to resist three shots from a 9-millimeter handgun) to Level 10 (must be able to resist at least one shot from a 0.50-caliber rifle).

Some manufacturers offer engineered products designed to withstand specific natural and man-made disasters. These products resemble their conventional counterparts but meet the test criteria for FEMA safe room doors, for DoD blast resistance, or the varying levels of bullet resistance as defined by UL 752. Since some of these products are likely unfamiliar to many architects, manufacturers who offer robust technical and customer support have an advantage, says Steve Peterman, director of sales and marketing, AMBICO Limited.

“We support architects by offering superior products and service to meet the often demanding performance requirements associated with resilient design,” he says.